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Biomedical subjects

L Martini

Publications and source records attributed to L Martini.

At least 181 records · Page 10Linked to original sources
PubMed1983

Influence of adrenalectomy and ovariectomy on gonadotrophin secretion.

In order to gain additional information on the effects exerted by adrenal hormones on gonadotrophin secretion, adult female rats have been submitted concomitantly to adrenalectomy and ovariectomy; ovariectomized animals with intact adrenals served as controls. Serum levels and pituitary concentrations of LH and FSH have been measured on post-operation days 1, 2, 7, 14 and 28. It has been found that ovariectomy, when performed alone, induces a progressive but delayed release of LH and a rapid and constant release of FSH. Ovariectomy exerts only minor effects on the concentrations of pituitary LH, while providing a strong stimulus to the intrapituitary accumulation of FSH. Adrenalectomy, superimposed on ovariectomy, advances the release of LH, and at the 4-week interval, increases serum levels of this gonadotrophin to well above those found in animals submitted only to ovariectomy; the absence of the adrenals does not significantly alter the release of FSH. Adrenalectomy, added to gonadectomy, strongly facilitates the accumulation of LH in the anterior pituitary, but decreases the resynthesis of FSH. In conclusion, these data suggest that one or more factors of adrenal origin may: (1) inhibit the release of LH without affecting the release of FSH; (2) prevent the post-gonadectomy accumulation of LH in the anterior pituitary and facilitate the re-accumulation of FSH.

Adrenalectomy↗
PubMed1982

Effect of opioid peptides on gonadotrophin secretion.

The intraventricular injection of 25 micrograms of Methionine-Enkephalin (Met-Enk) induces a significant increase of serum LH levels in long-term ovariectomized rats 15, 30 and 60 min following administration. The synthetic Met-Enk agonistic analogue [D-Ala2] methionine-Enkephalinamide ([D-Ala2]Met-Enk) also enhances significantly serum LH levels at 30 and 60 min; under the same experimental conditions neither Met-Enk nor [D-Ala2]Met-Enk modifies serum levels of FSH following intraventricular injections into ovariectomized animals. It is concluded that, under particular circumstances, opioid peptides of the Met-Enk family may stimulate LH release.

Animals↗
PubMed1982

Effects of orchidectomy and sex steroids on vasopressin response to dehydration.

The secretion of vasopressin has been shown recently to be influenced by gonadal steroids. To further evaluate the relevance of sex steroids in the control of vasopressin secretion, the vasopressin response to dehydration has been studied in normal, castrated and sex-steroid treated castrated male rats. Short-term (3 weeks) castration did not modify the vasopressin response to 48 h of water deprivation. Long-term (10 weeks) castration, on the other hand, consistently reduced the vasopressin response by more than 50%. In both cases, the osmolality was unaffected. Treatment of long-term castrated rats with testosterone, dihydrotestosterone, or oestradiol increased the vasopressin response to dehydration towards normal control levels. However, only oestradiol could restore it to and beyond normal levels, although all three steroids were given in doses that were equipotent in bringing back to normal the plasma LH levels of the castrated animals. Angiotensin-II generation may indirectly be augmented by oestradiol treatment and this may account for the effect of oestradiol here reported. No such mechanism, however, may be invoked in the case of androgens; a direct modulatory effect at the hypothalamic level is postulated for explaining their influence on vasopressin secretion.

Age Factors↗
PubMed1982

Role of the organum vasculosum laminae terminalis in the control of gonadotrophin secretion in rats.

The organum vasculosum laminae terminalis (OVLT) was destroyed by radiofrequency lesions in regularly cycling and in long-term ovariectomized adult rats. After OVLT lesion practically all cyclic females (16 out of 22) became dioestrous, as indicated by vaginal smears. At the time of killing these animals (8 days after the lesion) serum LH levels were undetectable, while serum FSH was as low as in cyclic animals in dioestrus. In the few OVLT-lesioned animals which exhibited some sort of oestrous cyclicity, serum LH showed a small subphysiological increase at pro-oestrus; this was not accompanied by a parallel increase in serum FSH and in these animals a delayed peak of FSH occurred on the day of oestrus. Ovariectomized rats bearing OVLT lesions had serum titres of Lh and FSH as high as those of ovariectomized control rats. It is suggested that the OVLT may play a role in the control of the cyclic release of gonadotrophins but is not involved in the tonic regulation of gonadotrophin secretion.

Animals↗
PubMed1982

Role of the subcommissural organ in the control of gonadotrophin secretion in the female rat.

Thermal lesions were placed in the subcommissural organ (SCO) of female rats with normal cycles and long-term ovariectomized rats. In normal female rats SCO lesions disrupted the oestrous cycle in more than half of the animals, the majority of which entered a state of prolonged dioestrus. In these animals, serum gonadotrophin levels were similar to those of rats with regular cycles on day 2 of dioestrus. In animals in which the oestrous cycle was maintained, a delayed LH surge occurred on the day of pro-oestrus and the pro-oestrous FSH surge was absent. The usual increase in FSH on the day of oestrus was present. Lesions in the SCO did not change the high gonadotrophin levels typical of ovariectomized animals. These results suggested that the SCO may play a role in the control of the cyclic but not the tonic release of the gonadotrophins. In particular, it appears that the SCO might be involved in the regulation of the hypersecretion of FSH during the day of pro-oestrus.

Animals↗
PubMed1981

Role of the subfornical organ (SFO) in the control of gonadotropin secretion.

Radiofrequency lesions have been placed in the subfornical organ (SFO) or normally cycling and of long-term castrated female rats. The data have shown that, in normal female rats, SFO lesions bring about a disruption of estrous cyclicity in a large number of animals, the majority of which enter a state of prolonged diestrus. In these animals, serum gonadotropin levels are similar to those of regularly cycling animals in the second day of diestrus. In the animals in which estrous cyclicity was still present, an LH surge occurred which was regular in timing and magnitude. On the contrary the proestrous FSH surge was absent, but the usual FSH elevation of the day of estrus was present. SFO lesions were not able to change the high gonadotropin levels typical of the post-castration situation. These results suggest that the SFO may play a role in the control of the "cyclic" but not of the "tonic" release of the two gonadotropins. In particular, it appears from the results that the SFO might be involved in the regulation of the hypersecretion of FSH which occurs during the day of proestrus.

Animals↗
PubMed1981

Neurotensin inhibits LH release.

The present studies were designed to assess the effect of neurotensin on the release of LH, FSH, and prolactin in long-term castrated female rats. The animals were implanted in the lateral ventricle of the brain wih a cannula to allow the administration of either neurotensin or the vehicle. The peptide (30 microgram, dissolved in saline) or the control saline solution was injected intraventricularly in a volume of 10 microliter following pentobarbital anesthesia. Blood samples were collected at sacrifice 15, 30 and 60 min after injection. A significant decrease of serum LH levels was already present in neurotensin-treated animals at 15 min, and was maintained up to the end of the experiment. This decrease was not accompanied by any change in FSH or prolactin secretion. The results suggest that this tridecapeptide participates in the control of LH release and provide new data on the separate control of the release of the two gonadotropins.

Animals↗
PubMed1980

Cholinergic inputs to the amygdala and the control of gonadotrophin release.

Adult female rats castrated 4 weeks before were implanted bilaterially into the basomedial area of the amygdala with drugs known to mimic or to counteract the actions of acetylcholine. The animals were sacrificed at different time intervals after the implantation of the different compounds, and serum levels of LH and FSH were measured by radioimmunoassay. The data obtained indicate that the intra-amygdalar implantation of the muscarinic blocker atropine induces a significant increase of the release of LH without altering FSH secretion. The implantation of two cholinomimetic drugs, pilocarpine, an almost pure muscarinic agonist, and carbachol, which possesses both muscarinic and nicotinic properties, exerted an inhibitory effect only on LH release. On the contrary, the intra-amygdala placement of the nicotinic blocker mecamylamine was followed by an increase of FSH with no changes in LH. These observations may suggest that cholinergic signals reaching the amydgala may be of some relevance in the mechanisms controlling gonadotrophine secretion. Muscarinic receptors seem to play an inhibitory role in the regulation of LH secretion, while nicotinic receptors seem to modulate in an inhibitory way FSH release.

Amygdala↗